This article introduces a novel class of ∆h-truncated exponential-based Hermite polynomials and examine their fundamental properties and structural identities. We derive generating functions, recurrence relations, and explicit formulas, along with summation identities. The study further uncovers connections with the monomiality principle, offering insights into their underlying algebraic framework. In addition, an operational formalism is developed, and symmetric identities are established to enhance the theoretical foundation of these polynomials.

Oxide dispersion in high-entropy alloy (HEA) improves mechanical properties, corrosion resistance, and high-temperature oxidation. Several studies have been reported on oxide-dispersed high-entropy alloys prepared by Spark plasma sintering and hot pressing, but only a few on coating. This study aims to investigate a novel Fe-free Co1.7 Cr0.4Ni2.5Al2.4 Nb0.23 HEA dispersed with oxide (1 wt % Y2O3) for bond coat application in the thermal barrier coatings (TBC) System. The elemental powders in desired stoichiometry along with yttria were milled for 5 h in a planetary ball mill with a ball-to-powder ratio of 10:1 at a speed of 300 rpm followed by heat treatment at 1050 C for 1 h in argon. ODHEA bond coat and yttria-stabilized zirconia (YSZ) topcoat was coated by high-velocity oxygen fuel (HVOF) and air plasma spray on a nickel superalloy substrate, respectively. The coating shows the formation of FCC, BCC and Laves phase. The hardness and Young's modulus for the coating were approximately 610 HV and 172 GPa. Good oxidation resistance with an average TGO layer thickness of less than 7 μm was observed after 100 h of isothermal oxidation.

Here, a planar design of a filtering antenna is presented. The design mainly comprises a semi-circular substrate integrated waveguide (SIW) cavity as a driven element and a rectangular parasitic patch with loaded metallic vias. The coax feed is used to excite the SIW cavity and the cavity excites the rectangular patch by a coupling mechanism. The loaded four metallic vias help realize the gain characteristic's sharp selectivity with radiation null at both edges of the operating band. The simulated investigation shows that broadband response is achieved by using such a topology. The measured results show a broad band response of 7.90 % impedance bandwidth with a flat realized gain performance of 7.34 dBi in the entire operating band. The proposed design offers attractive features such as small foot prints, high gain, small cross polarization, high selectivity, and a high front-to-back ratio.

In aerospace applications, engine parts, especially those around the rotor blade tips, are coated with an abradable seal, a specific material layer. Its design produces a tighter seal without harming the blades by allowing it to wear down or “abrade” somewhat when the blade tips come into contact. In turbines and compressors, this reduces gas leakage between high- and low-pressure zones, increasing engine efficiency. Abradable seals are crucial to contemporary jet engines because they enhance performance and lower fuel consumption. The materials selected for these seals are designed to balance durability and abrasion resistance under high temperatures and speeds. Metal matrix, oxide particles, and porosity are the three most prevalent phases. An ideal mix of characteristics, such as hardness and erosion resistance, determines how effective a seal is, and this is accomplished by keeping the right proportions of elements in place throughout production. The primary objective of this research is to optimize abradability by utilizing various FEM tools to simulate the rub rig test and modify testing parameters, including Young’s modulus, yield stress, and tangent modulus, to analyze their impact on the wear behavior of the abradable seal and blade. Two microstructure models (CoNiCrAlY–BN–polyester coating) were found to perform optimally at porosity levels of 56% and 46%, corresponding to hardness values of 48 HR15Y and 71 HR15Y, respectively. Changing factors like yield stress and tangent modulus makes the seal more abrasive while keeping its hardness, porosity, and Young’s modulus the same. Furthermore, altering the Young’s modulus of the shroud material achieves optimal abradability when tangent modulus and yield stress remain constant. These findings provide valuable insights for improving material performance in engineering applications. To improve abradability and forecast characteristics, this procedure entails evaluating the effects of every single parameter setting, culminating in the creation of the best abradable materials. This modeling technique seems to provide reliable findings, providing a solid basis for coating design in the future.

Large portion of wind turbine blade is sandwich construction made out of glass fiber/epoxy composite face sheet with foam core. The objective of the current study is to evaluate alternate core materials suitable for blade shell sandwich applications for low cost and low weight. Various commercially available core materials are evaluated analytically for panel level buckling performance and aerial weight for relative comparison of core material. Based on structural and cost analysis, Webcore structural core material is selected for blade shell application and experimentally evaluated for its properties, such as density, shear modulus, compression modulus and tensile modulus, to compare with currently used PVC foam core. Buckling tests of sandwich panel are conducted to evaluate core materials performance for wind blade application. Webcore materials proved to be better candidates for wind blade applications as compared to PVC foam core.

There are attempts to develop a hybrid (S-glass–carbon) composite fan blade which can show excellent damage resistance under bird strike kind of loading. Some part of the carbon fiber composite blade is to be replaced with S-glass and to achieve this, carbon–glass joints need to be optimized. The main technical challenge in this, is the robustness of the interface region between S-glass and carbon plies. The interface region optimization in terms of ply layups and overlaps has been performed and a few promising cases of interlock configurations have been proposed in this context. As part of this interlock region structural evaluation task, representative composite coupons were made, and bird strike impact tests were performed. This article presents the bird strike analysis results of these interlock ply-by-ply coupons and the correlations of these analysis results with the actual bird strike test results performed on these coupons. Overall analysis to test results correlation has been satisfactory and detailed comparisons are shown in this article. The coupon-level bird strike analysis methodology was enhanced by including the resin pockets that results in the interlocking regions. The understanding obtained from this work will be used as guideline for designing and validating the hybrid composite blade for aircraft engines.

This study introduces a new class of ∆h Legendre-Laguerre-Appell polynomials, constructed through the synergy of the monomiality framework and operational calculus. A comprehensive exploration is carried out, beginning with the formulation of their generating function, followed by the derivation of explicit representations and recurrence schemes. Notably, a determinantal structure for these polynomials is also established and illustrated through representative examples. The work further investigates how this polynomial family interrelates with well-known ∆h-variants of classical polynomials, including the Bernoulli, Euler, and Genocchi types. Through these connections and properties, the results not only deepen our understanding of the algebraic and analytic behaviour of the ∆h Legendre-Laguerre-Appell polynomials but also highlight their potential applications in broader areas of discrete mathematics and operational theory.

An aircraft engine’s fan blades are one of the most important parts of the engine. Bird strikes on fan blades have always been an issue, as bird parts can strike other parts of the engine, potentially causing more damage. It is impossible to avoid being struck by a bird entirely. However, finite element analysis can be used to optimize the design of blade so that the overall impact of a bird on a jet engine is reduced. Even though current composite blades can withstand the impact of a bird strike, some delamination failures have been observed on the blade’s trailing edge side, probably due to vibration bending modes. Instead of the single fiber composite blade that is currently in use, this research proposes using two fibers (Carbon and Glass). For this to be possible, two fiber joints must be designed properly at different locations on the blade. At crucial joint locations, the minimum inter-laminar strain level was used as the design criteria. Blade deformation is simulated using coupon and sub-element level finite element analysis (FEA) models with appropriate boundary conditions with in-built hybrid joints inside. The first stage of this project involved using the Ansys Parametric Design Language (APDL) and linear static analysis to create coupon models for combinations of joint positions. In the present work, dynamic bird strike analysis on sub-element level models was performed with various joint location combinations. The best joint configurations based on static and dynamic analysis results will be suggested for use in the composite blade to prevent delamination.

It has been observed that when the rotating composite fan blade in an aircraft engine is subjected to high-velocity bird strike, the damage is generally seen on/near the trailing edge even though the impact is happening on the leading edge. This behavior of the blade is tentatively attributed to the stress wave propagation, but there is a strong need for deep understanding to be developed on this. This report talks about the efforts to understand the reasons for trailing edge strain hot spots happening due to bird strike impact on the leading edge. In this context, fundamental plate-level bird impact and simple wavelet excitation studies were performed along with the stress wave propagation studies. The studies show that the stress wave propagation could be attributed up to some extent to the high strain spots appearing on/near the trailing edge. The studies also showed that these strain hot spots can be avoided by applying some innovative techniques.

This paper presents a novel design of a compact, low-profile, Substrate Integrated Waveguide (SIW) based Multiple-Input Multiple-Output (MIMO) antenna operating at the 2.45 GHz Industrial, Scientific, Medical (ISM) band. The antenna consists of two quarter-mode (QM) SIW cavity resonators and one diamond-shaped complementary split ring resonator (CSRR) slot etched on each cavity. The unique feature of this geometry is the ability to tune the operating frequency of the dominant mode to a lower frequency range by rotating the slot in the range of 0°-180°. The excitation of both cavities is achieved using microstrip feedlines. By placing both cavities in an orthogonal configuration, a significant isolation level of around -28 dB between the two ports is achieved. MIMO metrics parameters, including the envelope correlation coefficient (ECC) and diversity gain (DG), mean effective gain (MEG), and channel capacity loss (CCL) have been investigated, validating the MIMO capabilities of the proposed design. Due to its compact dimensions, minimal profile, and alignment with the ISM band, the antenna lends itself seamlessly to integration with healthcare devices, facilitating its deployment within Wireless Body Area Network (WBAN) applications. The robust performance of the antenna in the vicinity of the human body has been verified by investigating the S11 against frequency on different body parts such as the arm, head, and chest of the voxel phantom. The proposed design has been experimentally tested, and the measured responses closely agree with the simulations. The antenna exhibits a front-to-back ratio better than 10 dB and peak measured gain values of 5.0 dBi.

Bird strike has been a perennial problem for all airline companies in the world. It is the most important design criteria for the fan blades of an aircraft engine. As it is not possible to manufacture and test aircraft engines again and again for small design changes, through the simulation analysis, it is possible to study the ways to reduce the impact of the bird on a jet engine by using appropriate design and manufacturing methods for the blade. This research suggests using two fibers (hybrid) in place of the single fiber composite blade which is currently in use to reduce the delamination issues. In the first stage of this research, representative composite coupon models for combinations of hybrid fiber joint positions were created and linear static analysis was performed. For the validation of simulation methodology, a few coupons were manufactured and tested in the laboratory. Further, dynamic bird strike analysis on sub-element level models was carried out in the second stage with various joint location combinations. Next, the plate-level representative blade model was designed with the original dimensions of the aircraft engine fan blade, and bird strike analysis was performed. The behavior of the representative plate with hybrid interface was studied, and the levels of inter-laminar shear strain were checked, by varying the joint location of the two composites. Some of the shortlisted cases do show significant promise of being damage tolerant under bird strike loading.

Upgrading abradable or wearable coatings in the high-temperature zone of aero engines is advised to increase the efficiency and high-density power in gas turbine engines for military or commercial fixed-wing and rotary-wing aircraft. The development of these coated materials is also motivated by minimization of the number of failures in the blade, as well as increasing their resistance to wear and erosion. It is suggested that abradable coatings or seals be used to accomplish this goal. The space between the rotor and the shroud is minimized thanks to an abradable seal at the blade’s tip. Coatings that can withstand abrasion are often multiphase materials sprayed through thermal spray methods, and which consist of a metal matAzmeerix, oxide particles, and void space. The maintenance of an ideal blend of qualities, such as erosion resistance and hardness, during production determines a seal’s effectiveness. The objective of this research is to develop microstructure-based modelling methodology which will mimic the coating wear process and subsequently help in designing the abradable coating composition. Microstructure modelling, meshing, and wear analysis using many tools such as Fusion360, Hyper Mesh, and LS-Dyna, have been employed to develop an abradable coating model and perform wear analysis using a simulated rub rig test. The relation between percentage composition and morphology variations of metal, oxide, and voids to the output parameters such as hardness, abradability, and other mechanical properties is explored using simulated finite analysis models of real micrographic images of abradable coatings.

Drones have been implemented for several applications around the world due to its robust technology and ease of operation. The incorporation of advanced technologies into Unmanned Aerial Vehicles (UAVs) platforms have enabled many practical applications in precision agriculture (PA) over the past decade. In this project, we are considering drones that are implemented for agricultural purposes to spray the fertilizer without the need of a person nearby. This project uses an innovative Hexa-copter design with a new streamlined structural geometry. This design is validated for its successful implementation through stress analysis using ANSYS and also through suitable material selection for fabrication. The drone parts are built by selecting four other materials for different components. The outcome of this research provides suggestions, maximum/minimum stress levels and future directions to overcome challenges in optimizing operational proficiency of the drone.

Bird strikes have long been a source of concern for all airlines across the world. It is the most significant design criterion for aircraft engine fan blades. As it is not practical to manufacture and test aviation engines repeatedly for minor design modifications, simulation analysis can be used to investigate strategies to reduce the influence of a bird strike on a jet engine by employing proper design and manufacturing processes for blades. This study proposes using two fibers (hybrid) instead of the single-fiber composite blade presently in use to address delamination problems. As an idea validation test, the coupon-level analysis results are validated using a four-point bend test of similar-size coupons. Following this validation, dynamic analysis is used to investigate the impact behavior of a rectangular plate subjected to a bird strike. The current research focuses on analyzing bird strikes on a hybrid composite fan blade using blade-level models. This study concentrates on the position of the bird’s impact and the joint region length of two materials. The results show that the joint region with a 40% length of glass composite shows the optimum level of normalized interlaminar shear strain in all three impact locations.

The use of laminated fiber reinforced composite structures is limited by the delamination type of failure under various types of loading. Early researchers did some attempts to come out with a methodology for modeling delamination behavior under static and dynamic impact loading. These early attempts were mostly talking about the unidirectional laminates due to difficulties in modeling the multi-directional laminates for delamination behavior. The real world, however, use the multi-directional laminates only due to their distinct advantages. This article is a sincere attempt to develop a mode I delamination prediction process for multidirectional carbon fiber composite laminates (with various interfaces like 0-0, 45-45 and 90-90) under quasi-static and dynamic impact loading. For modeling the behavior under quasi-static loading, ANSYS software is used with its in-built contact definitions based cohesive zone model. The mode one type failure tests were conducted on multidirectional carbon fiber composite coupons as per available standards and their load displacement behavior is validated using the FEA cohesive zone models. The mode I test coupons are modeled as per the real specimens and the delamination failure is studied/validated in the simulation. For dynamic impact type loading, LS-DYNA software is used with its the inbuilt tiebreak type contact option capabilities which are almost similar to that of cohesive zone elements. The conclusions show that cohesive zone models can match the delamination behavior in this kind of composite materials under static and dynamic impact type loading. The modeling methodology/process needs to be further improved through application and validation with different geometries and loading rates for both situations to make it more robust and ready for applications to aerospace composites.

Asymmetrical Four Point Bend test method is proposed for measurement of interlaminar shear strength in continuous fiber reinforced ceramic composites. The current standard ASTM test method (ASTM C1425) for interlaminar shear strength of composites uses a double edge notched compression (DNC) coupon. Large variation in measured strength is observed with the standard ASTM test method, possibly due to machining variability and damage at the notches. The proposed test AFPB method for ILSS is adapted from ASTM C1469 Standard Test Method for Shear Strength of Joints of Advanced Ceramics. This test method does not require any machining of notches and the sample size requirement is much smaller than the ASTM test method. The shear loading in this method is similar to the standard short beam shear test (ASTM D2344) with higher shear to tensile ratio compared to SBS with AFBP. Using finite element analysis, coupon geometry and the distance between the loading and support pins was optimized to maximize shear and minimize tensile and compressive stresses on the specimen. It was found that the variability in the measured ILSS strength was lower with this method compared to the ASTM standard method using the DNC specimen. In addition, the value of ILSS measured using AFPB method was found to be consistently higher than that measured using DNC coupons. It was also found that specimen preparation (cutting, polishing, etc.) did not have significant effect on the measured strength.

Most of the ply-by-ply laminated composite structures are constrained by delamination type of failure under different loadings. There were attempts to develop modeling methods for delamination under static and dynamic loads in the past. Most of the earlier attempts are focused on the unidirectional laminates because of complexity involved in the multi-directional laminates. However, in the real life, many time multi-directional laminates are used. This paper is an effort to create such modeling methodology for multi-directional carbon composite laminates (with 0–0, 45–45 and 90–90 interfaces) under static and dynamic loads. For modeling the static load case, Ansys software is used with the in-built contact based cohesive zone material model. The mode II experiments were conducted on multi-directional carbon composite coupons as per ASTM standards and the load displacement behavior is verified using the finite element analysis (FEA) cohesive zone models (CZM). Mode II test coupons are modeled in 3D, and the delamination is captured in the analysis simulation. For dynamic loading, LS-Dyna is used with the in-built tiebreak contact-Dycoss-Option 9 capabilities which are almost similar to the cohesive zone elements. The results indicate that cohesive zone models can predict the delamination in the kind of materials under static and dynamic loading conditions. The modeling methods will be further improvised for both situations to make it more robust and ready for applications to aircraft engine components in consideration of delamination.

Application of digital image correlation technique for full field strain characterization has gained widespread interest. However, characterization of the strain and damage at very small length scales using this technique is still difficult and development in this regard would add a great value in understanding the material behavior, particularly for in-homogeneous materials such as composites. This article describes the work done primarily on continuous fiber reinforced polymer composites and ceramic matrix composites, towards applying the digital image correlation (DIC) technique at very small length scale, of the order of 100-200 lm. A novel technique was developed to generate a fine and randomly distributed speckle pattern. Actual examples of the application of digital image correlation at small length scales for strain and damage characterization are briefly described such as ply level strain measurement near ply drop in a fiber reinforced composite, local carbon-glass fiber joint strain measurement in hybrid composites, and short beam shear strength validation using ply level strain measurement in carbon glass fiber joints in hybrid composites. Limitations of digital image correlation technique for small scale strain measurement are also discussed.

Recently there have been many successful attempts to implement the use of fiber-reinforced composite structures in the commercial aircraft engines. The author has been part of these efforts while working in the aviation industry. This article describes these efforts to design, analyze, manufacture, and implement the composite structures inside the low-pressure and low-temperature zones of the engine. Very innovative out-of-the-box design methodologies were used to design these components. These efforts elaborate on the design, optimization, and improvement of composite fan blade, composite fan platform, and composite booster blade inside the engine. It focuses on structural design, the aerodynamic efficiency, and specific fuel consumption improvement efforts along with the usual reduction of weight targets. This work successfully demonstrates the systematic steps in design and implementation like preliminary coupon-level simulations, coupon-level manufacturing, coupon/prototype testing, and final part-level simulations followed by part test.

Improvised sealing methods are required between rotating and stationary parts in aircraft engines to improve the engine performance significantly by improving thermal efficiencies. To achieve this, use of abradable coatings/seals are proposed. With an abradable seal, blade tip incurs into the shroud, thereby reducing the gap between rotor and the shroud to a minimum. Abradable coatings are generally multiphase materials applied using thermal spray techniques. The most common three phases are metal matrix, oxide particles, and porosity. Effectiveness of seal is determined by optimum combination of properties like erosion resistance and hardness; and this is achieved by maintaining proper combination of the ingredients while manufacturing. The present study intends to develop theoretical/modeling approach to study these materials and develop design and property prediction capability in order to come up with best abradable materials. This modeling approach seems to provide consistent results and these results can be used as a reliable starting point in further coatings design.

As part of the composite compressor blade of aircraft engine concept study, a technical feasibility of replacing the current Titanium blades with fiber reinforced composite ones is evaluated here. This can result into substantial weight saving and may result in some cost saving too. In addition to the regular design criteria like stress and frequencies, survival under bird strike loading is also most important criteria. To evaluate composite blades made with different possible material systems under bird strike loading, is a time consuming and expensive task. In order to come up with a simplified method to evaluate the various possible cases, flat sub-element coupons are designed, fabricated and tested under bird strike loading in a real test facility. This simplified method is easy to use, fast and cost effective. This method generates strain allowable for different cases under bird strike loading using the combination of actual bird strike tests and the bird strike analysis of the same panel models in LS-Dyna software. This paper presents the results of the analysis and testing of these laminated composite panels and test analysis correlation. It is shown that strain allowable are easy to extract from the test-analysis correlation data.

Attempts to add the advanced technologies to aerospace composite structures like fan blade have been on in recent times to further improve its performance. As part of these efforts, it has been proposed that the wavy trailing edge could be used in the blade to reduce the noise level. It has been also proposed that it’s structural feasibility could be studied by fabricating coupons representing blade like boundary conditions and mimicking max strain contours of wavy trailing edge of blade and testing them. Suitable size coupons (baseline flat and ones with wavy edge) were designed, and appropriate boundary condition was suggested for tests. The four-point bend tests were performed on baseline flat and wavy edge coupons and after analyzing the results it was concluded that some wavy edge configurations coupons do show some knock down in the failure load/strain but the optimized wavy edge configuration coupons show almost no knockdown (within scatter) in the failure load/strains. This leads to the conclusion that the wavy edge configuration under consideration has sufficient structural integrity as per the representative coupon test.

Since the last decade, gearbox systems have been requiring increasing power, and consequently, the complexity of systems has escalated. Inevitably, this complexity has resulted in the need for the troubleshooting of gearbox systems. With a growing trend of health monitoring in rotating machines, diagnostic and prognostic studies have become focused on diagnosing existing and potential failures in gearbox systems. In this context, this study develops the architecture of the cloud-based cyber-physical system (CPS) for condition monitoring of gearbox. Empirically collected vibration signals of gear wear at various time intervals are processed using empirical mode decomposition (EMD) algorithm. A Euclidian-based distance evaluation technique is applied to select the most sensitive features of car gear wear. Artificial neural network (ANN) is trained using extracted features to monitor the gearbox for the future dataset. Comparison of the performance results revealed that the ANN is superior to the other EMD methods. The present methodology was found efficient and reliable for condition monitoring of industrial gearbox.

In many structural applications, either a notch or a hole is used for some specific design intent. The notch could be contained within the plane of structure, or it could be partially located along the edge of the structure. Although theoretical formulae are available for computing the stress variation along the section passing through a simple hole or a notch, for complicated structure or loading conditions, it becomes difficult to evaluate the stress variation. One such example of complicated structure is proposed wavy trailing edge on the composite fan blade where waviness on the edge of blade could be in-plane as well as out of plane. It is important that for evaluation of stress variation in these type of structures, a methodology (i.e., failure criteria based on notch or hole strength) should be developed which will help in predicting the mechanical behavior/failure load of new designs of these structures. Based on preliminary coupon bending tests (coupons with and without wavy trailing edge) and FEA analysis of the coupon models, the characteristic distance from the edge is evaluated and later used to predict the failure for new wavy trailing edge designs for composite fan blade.

Attempts to add the advanced technologies to aerospace composite structures like fan blade have been on in recent times to further improve its performance. As part of these efforts, it has been proposed that the blade morph feasibility could be studied by building and optimizing asymmetric lay up of composite plies inside the blade which will help generate enough passive morphing between max cruise and climb conditions of the flight. This will have a direct efficiency (Specific Fuel Consumption) benefit. This research describes the various ideas that were tried using in house-developed lay-up optimization code and Ansys commercial software to study the possibility of generating enough passive morphing in the blade. In the end, this report concludes that the required degree of passive morphing could not be generated using various ideas with passive morphing technology and only up to some extent of morphing is shown to be feasible using the technologies used here.

To prepare students for various competitive examinations like GATE, GRE etc it is a challenging task as it requires basic understanding of the courses. Also it needs lots of practice to solve complex problems. So, in this paper the use of three online tools: Gate Test series, Answer Garden and Polls Everywhere is been described for the course operating system. As Operating System course has higher weight-age in various competitive examinations like GATE. So, we choose this course as a case study to apply online tools. Finally the comparative analysis has been done for MCQ-Test1 marks where these tools were not used and MCQ-Test2 which was conducted after applying these tools.

In most of the aerospace laminated composite structures, thickness variation is achieved by introducing the ply drops at the appropriate locations. Ply drop means the resin rich regions created due to abrupt ending of individual plies within the set of plies. This research is focused on understanding and quantifying the effect of these ply drop regions on the mechanical performance of the aerospace composite structures. This is achieved here by designing the appropriate coupons (with and without ply drops) and analyzing them using finite element analysis. Some typical designs of coupons were manufactured using aerospace grade carbon composite materials, and then tested under four-point bend, cantilever and short beam shear tests to check and validate the effect that was seen in the analysis. It is concluded here that allowable failure strains are different for with and without ply drop cases by a significant amount.

There have been many attempts to redesign the aerospace composite structures in recent times to further improve their performance and reduce the weight. As part of these efforts, it has been proposed here that lightweight polymeric foam can be used as an embedded insert inside the fiber reinforced composite structure to further reduce its weight. The target application here is composite fan blade of aircraft engine This paper describes the analysis led design (FEA) and experimental efforts to optimize the shape of this embedded foam insert inside the composite structure under both representative static and dynamic loading so that weight reduction is achieved without affecting the structural performance of the aerospace composite structure. Different geometrical parameters like taper of foam tip, blunting level of the foam tip, use of dual or multiple foam inserts, use of continuous ply layer and other parameters like use of softer material like glass near foam tip, thickness of adhesive (which is used to bond foam with carbon composite) are investigated and their effect on the level of shear stress near the foam tip has been observed. The level of shear stress near the foam insert tip is found to be the major indicator of the possible crack initiation near tip. This study helped optimize the shape of the foam insert inside the composite structure to avoid the initiation of cracks, which is validated by manufacturing the lab level carbon fiber epoxy composite specimens with optimized foam insert geometry and testing them under representative staggered four point bend boundary conditions.

Sensing, gaging and locating the structural damage inside the wooden wall structure using vibration response is a proven technology and many research articles are published in this thematic area. The damage detection is usually carried out by monitoring and assessing damagesensitive parameters such as resonant frequencies and operating deflection shapes. However, in this article we propose a novel methodology based on FRF curvature and transmissibility based on the vibration response data as a quantitative parameter to detect and locate damage inside a wall structure. Mock damage was created in one of the structural wooden partition wall of a specially built room and its vibration response was measured. Damage-sensitive factors were taken out from the frequency response data and applied for gaging the damage quantitatively. For locating the damage region, quantitative parameters method, i.e. broadband FRF curvature and transmissibility methods were utilized. These techniques if commercialized, can save billions of dollars in pest control.

Termites infestation is a big problem for trees. It is also very difficult to find the trees with termite damage. It is essential to find the trees with initial level of termite damage so that the trees can be treated with suitable available treatments. It is proposed here a new technique using vibration analysis which can detect the termite damage inside the tree trunks by just performing very simple vibration experiment. This method is cheap, efficient and can potentially save large number of trees from dying due to termite infestation. By performing laboratory level experiments, this research proves the feasibility of this simple technique of damage detection in trees.

This paper describes the application of vibration modal analysis for detecting, monitoring and locating damage inside a wooden wall structure, by evaluating damage-sensitive parameters such as resonant frequencies and operating deflection shapes (ODS). Artificial damage was created in one of the walls of a specially constructed room. The wall was excited using an impact hammer and its frequency response was measured with a laser vibrometer. Damage-sensitive parameters were extracted from the frequency response and utilized for assessing damage, both qualitatively and quantitatively. Resonant frequency shifts and changes in ODS were used for detecting and monitoring the progression of damage, qualitatively. These methods make direct use of FRF data and mode shapes for damage assessment, which will help a lot in identifying damaged walls.

Most laminated composite structures are limited by delamination failures under different kinds of loading. There have been many attempts to develop modeling methodology for delamination under static and dynamic loading. Most early attempts focused on unidirectional laminates due to complexity involved in multi-directional laminates. However, in the real world, most of the time, multi-directional laminates are used. This paper is an attempt to develop such modeling methodology for multi-directional carbon composite laminates (with 0-0, 45-45 and 90-90 interfaces) under static and dynamic loading. For modeling the static loading case, ANSYS15.0 software is used with its built-in, contact-based, cohesive zone material (CZM) model. The mode I and II experiments were also conducted on multi-directional carbon composite coupons as per ASTM standards and the FEA cohesive zone models were validated with experimental loaddisplacement behavior. Mode I and II test coupons are modeled and the delamination is captured in the simulation. For dynamic loading, LS-DYNA is used with built-in tiebreak contact- DYCOSS-Option 9 capabilities, which are similar to the cohesive zone elements. The results show that cohesive zone models can very well predict delamination in this kind of materials under static and dynamic loading conditions. The modeling methodology will be further optimized for both situations to increase robustness and ready for application to composite components in consideration of delamination.

The energy absorption characteristics of grid stiffened (isogrid) E-glass/Polypropylene (PP) composite panels were investigated under transverse load in both quasi-static and dynamic impact conditions. Under quasi-static loading, the panels loaded on rib side absorbed more energy than on skin side. Under dynamic impact, however, the panels loaded on skin side absorbed more energy than rib side. The energy absorbed was almost twice under dynamic impact than quasi-static loading. Vibration tests were also performed and it was concluded that the oscillations observed during the impact event could be attributed to structural resonances of the impactor, isogrid panel or both combined. Quasi-static test results were validated using Ansys finite element analysis software. LS-Dyna software is being used for validating the dynamic impact test results, and analyzing grid geometry variations for optimizing energy absorption. This study will lead to recommendations on the design and use in applications where impact energy absorption is important such as side doors of automobiles.

The energy absorption characteristics of grid stiffened (isogrid) E-glass/Polypropylene (PP) composite panels were investigated under transverse load in both quasi-static and dynamic impact conditions. Under quasi-static loading, the panels loaded on rib side absorbed more energy than on skin side. Under dynamic impact, however, the panels loaded on skin side absorbed more energy than rib side. The energy absorbed was almost twice under dynamic impact than quasi-static loading. Vibration tests were also performed and it was concluded that the oscillations observed during the impact event could be attributed to structural resonances of the impactor, isogrid panel or both combined. Quasi-static test results were validated using Ansys finite element analysis software. LS-Dyna software is being used for validating the dynamic impact test results, and analyzing grid geometry variations for optimizing energy absorption. This study will lead to recommendations on the design and use in applications where impact energy absorption is important such as side doors of automobiles.

The main focus of this paper is the optimization of geometry to maximize the specific energy absorption of E-glass/polypropylene isogrid composite panels under transverse quasi-static and dynamic impact loading using finite element analysis. The behavior of some of these grid-stiffened composite panels was also analyzed experimentally under high velocity impact loading, and the fluctuations observed in the load-time response during the impact event were attributed to structural resonances of the impactor, the isogrid panel or both combined. Parametric studies of varying the geometry (rib width and thickness; center-to-center distance between rib joints and skin thickness) to maximize specific energy absorption were performed. This study will help in recommending isogrid composite panels for the design and use in applications where impact energy absorption is important, such as in the side doors of automobiles. © 2005 Elsevier Ltd. All rights reserved.

The energy absorption characteristics of E-glass/PP grid stiffened composite panels under high velocity transverse impact loading has been investigated. Experimental results were validated using finite element analysis for both the skin and rib side loading. The results of test and simulations show that grid stiffened composite panels absorb lot of energy under dynamic impact load without catastrophic failure. The panels absorbed more energy when loaded on the skin-side than on the rib-side. The specific energy absorbed under dynamic impact loading was far greater than that for quasi-static loading. Vibration testing was used to analyze the cause of vibratory component in the impact response load-time history. Low velocity induced progressive impact damage in grid stiffened composite plates was also evaluated in a separate study using the vibration response measurement technique. This technique appears to be partially successful in detecting the various levels of induced impact damage in grid stiffened composites.

Transverse loading of grid-stiffened composite panels has significance in automotive crashworthy applications where optimizing the energy absorption is stipulated along with weight-critical restrictions. The phenomenon of failure and energy absorption in composites is complicated and this research is just a beginning to understand the behavior of grid stiffened composites under transverse quasi-static and dynamic load conditions. Authors, in their earlier publications have studied the energy absorption capabilities of E-glass/Polypropylene (PP) isogrid-stiffened composite panels under transverse loading, experimentally and validated the results using finite element analysis. The concluding part of this research is presented here which involves parametric studies of optimizing the grid geometry for maximizing the specific energy absorption under transverse quasi-static and dynamic impact loading. The parametric variations of skin thickness; width and thickness of ribs; and center-to-center distance between rib joints are performed in finite element analysis to maximize the specific energy absorption under transverse quasi-static and dynamic impact loading. The findings of this study will provide an optimized geometry of grid-stiffened composite panels which can impart highest specific energy absorption under transverse loading. This study will help in recommending the design and use of grid-stiffened composite panels in applications where impact energy absorption is important such as in the side doors of automobiles and highway side guardrails.

The energy absorption characteristics of E-glass/Polypropylene (PP) isogrid composite panels under quasi-static transverse load conditions have been investigated. Experimental tests and finite element simulations were performed for isogrid composite panels in three-point bending boundary condition. Results of tests and simulations show that loading the panels on rib side results in greater specific energy absorption along with larger displacements compared to skin side loading which is more abrupt. These results can be used to advantage in weight-critical automotive side impact crashworthy applications. Vibration response measurements which were used as a non-destructive tool for evaluating the quality of as-manufactured isogrid plates and monitoring induced damage in one of the plates are also presented. © 2005 Elsevier Ltd. All rights reserved.

Vibration techniques have been employed for detecting the presence and monitoring the progression of damage in structures. Pinpointing the location of damage is a more complicated and elaborate task. This paper presents modal analysis techniques for locating damage in a wooden wall structure by evaluating damage-sensitive parameters such as resonant pole shifts and mode shapes, residue and stiffness changes. Artificial damage (simulating termite degradation) was created in one of the walls of a specially constructed room. The wall was excited using an impact hammer and its frequency response measured using a laser vibrometer. Resonant poles (plotted in the s-plane) were used for identifying modes that are sensitive to damage, since not all modes are equally affected by the presence of damage. The damaged region was identified by visual comparison of the deformation mode shapes before and after damage. The modal residue and stiffness changes were also quantified for a better representation of the damage location. Copyright © 2004 Sage Publications.